An important feature of modem wireless telephony is enhanced wireless services. These are services for which the Mobile Switching Center (MSC) that does the switching for a call originating at a mobile station (MS) such as a cellular telephone requires the assistance of specialized Service Nodes (SN) that have the processing capability to perform the services. One class of such enhanced wireless services is interactive voice services. These services use information obtained from spoken input provided by the person originating the call to route or otherwise process the call. The services are termed "interactive" because they involve voice prompts from the telephone system and voice inputs from the user of the mobile station in response to the prompts. Examples of interactive voice services include
services in which voice input is used to select from a menu of choices, for example, between collect and credit card calls; PA0 voice-activated dialing services, in which the user speaks the number he or she wishes to reach; and PA0 services which use characteristics of the user's voice to authenticate the user to the wireless telephone system. PA0 the arrangement requires trunk 109 between serving MSC 107 and enhanced MSC 111. This both increases the cost of providing enhanced wireless services and prevents service providers who do not have such trunks available to them from providing enhanced wireless services. PA0 whether mobile station 103 is able to take advantage of the enhanced service depends on whether its serving MSC is connected by a trunk to enhanced MSC 111. Because that is so, roaming is not seamless when enhanced wireless services are involved.
All of the interactive voice services require specialized hardware and/or software voice input interpretation systems to handle the voice input. Moreover, the voice input is required to set up the call, and a voice channel must therefore exist for the interactive voice service before the call is set up.
FIG. 1 shows how enhanced wireless services such as interactive voice services are presently provided. Arrangement 101 shows a portion of a network for wireless telephony. Two kinds of information are involved in making a call in such a network: signaling information which coordinates the operation of the components of the network during the call, and the audio signals that the call carries once it is set up. In the following, the arrangements in the network for transporting signaling information will be termed signaling channels and the arrangements for transporting audio signals will be termed voice channels. In the figures of this Specification, signaling channels are represented by dashed lines and voice channels by solid lines. Arrangement 101 has an originating mobile station (OMS) 103 which has originated a call that requires an interactive voice service. The interactive voice service is specified by a sequence of digits dialed by the mobile station 103. The call origination goes via a signaling channel 104 provided by air interface 105 to serving MSC 107, the Mobile Switching Center which is currently handling the call origination for mobile station 103. Serving MSC 107 is permanently connected by trunk 109 to enhanced MSC (E-MSC) 111, a Mobile Switching Center which establishes connections to a number of Service Nodes 115 (1 . . . n) that contain the special-purpose hardware and software required for the enhanced wireless services. Trunk 109 provides a voice channel 108 between serving MSC 107 and enhanced MSC (E-MSC) 111. Serving MSC 107 is also connected by IS-41 signaling network 109 to enhanced MSC 111. Signaling network 109 provides signaling channel 112 between serving MSC 107 and E-MSC 111. Thus, when serving MSC 107 receives a call origination from a mobile station for a call that requires an interactive voice service, serving MSC 107 uses signaling channel 114 to send the dialed digits specifying the enhanced wireless service to enhanced MSC 111 and uses trunk 109 for voice channel 108. Enhanced MSC 111 then selects Service Node 115(i) required for the service and connects the trunk via local network 113 to the Service Node 115(i), so that voice channel 108 extends to Service Node 115(i). After Service Node 115(i) has performed the service, enhanced MSC 111 uses the result of the voice processing (for example, the digits specified by the voice input) to set up a call via public switched telephone network (PSTN) 107 or some other network to destination station 119. The call extends the voice channel 108 provided by trunk 110 via PSTN 117 to DS 119.
Arrangement 101 serves perfectly well to provide enhanced wireless services. It does, however, have two serious drawbacks:
It is an object of the techniques disclosed herein to overcome the above and other problems of current techniques for providing enhanced wireless services.